Sand transport in oscillatory sheet-flow; a literature review

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Chapter 1 Introduction

Introduction

1.1 Scope of the study

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Background

This literature review is part of the ongoing research on sand transport in oscillatory sheet-flow, as taking place at the coast during storms. Because sheet-flow corresponds to conditions of high shear stress, large amounts of sand are transported. Therefore it is an important part of the total sand transport (sheet-flow and suspended load).

Sand transport is a very important phenomenon in almost all coastal engineering problems. When a harbour is to be developed it is important to know how much sand is transported and in what direction, in order to prevent sedimentation problems in the entrance channel or in the harbour itself. Another example deals with coastal defence measures to prevent erosion of a beach. Either the use of coastal structures, like breakwaters, groynes etc., or a beach nourishment scheme requires information about the magnitude and direction of the general and local sand transport.

Unlike the sand transport in rivers, which can be assumed to occur in a merely one- dimensional, steady uniform flow, the sand transport at the coast is the result of a complex interaction of steady currents and a wave-induced unsteady oscillatory flow at an arbitrary angle to the current.

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Aim

In order to predict the resulting sand transport, many different models have been developed. The aim of this literature study is to present an overview of the models, that predict the unsteady sand transport in sheet-flow conditions. Some of the models are specifically derived for sand transport under sheet-flow conditions, while others have a more general basis. A comparison is made between the capability of the different existing models in predicting the sand transport in sheet-flow conditions. Moreover also the different experimental studies on sand transport in oscillatory flow are presented. As a result of the comparison the most encouraging direction for the ongoing research is determined.

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